The heart of a computer is a magnetic hard disk drive (HOD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk, and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing rapidly. In particular, HDDs have been desired to store more information in its limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components.
The further miniaturization of the various components, however, presents its own set of challenges and obstacles. Shields for the magnetic recording head of an HDD play a vital role in ensuring high recording densities. Trailing shields have been introduced to improve the magnetic gradient in the down-track direction, with side shields introduced to suppress the spread of magnetic fields in the cross-track direction. In such recording heads, improvement of the magnetic gradient is crucial in enabling high density magnetic recording.
In order to improve the signal-to-noise ratio (SNR) in HDDs, attempts have been made at improving the field gradient of perpendicular magnetic write heads. One such attempt has focused on increasing the permeability of the trailing shield of the magnetic head. However, with an increased areal density, the pole width of the write head generally decreases. A decrease in the width of the write head causes the permeability of the trailing shield to degrade, since a field applied region is reduced and the exchange field increases. This in turn reduces the field gradient of a magnetic head having a narrow track width. Therefore, it would beneficial to have a trailing shield with an increased permeability to counter this reduction due to narrow track width.